The present invention relates generally to electronic ballasts for fluorescent lamps. More particularly, this invention pertains to a compact fluorescent lamp and ballast assembly that provides a ballast housing having an air gap for isolating a ballast circuit from the heat generated by an energized lamp.
Several patents describe a compact ballast design having a heat shield for reducing the heat received by a ballast circuit from the attached lamp. For example, U.S. Pat. No. 5,691,598 issued to Belle, et al., describes a device that provides a thermal heat shield between the lamp tubes and the ballast circuitry. The thermal heat shield is positioned inside the ballast casing to attempt to reduce the temperature present around the ballast circuitry. Similarly, U.S. Pat. No. 4,490,649 issued to Wang describes a ballast having thermal baffle contained in a gas-tight envelope and positioned close to the miniature arc tube of the lamp to reduce the ballast temperature. Neither of these designs, however, describes the usage of an air gap between the lamp and the ballast to allow ventilation between the ballast and the lamp and to thermally isolate the ballast circuit from the heat generated by the lamp.
European Patent Application No. 66,855 A2 designed by Takteto describes a compact ballast having a housing that includes a partition plate to thermally isolate the ballast and a series of air ducts on the sides of the ballast housing for circulating the outside air with the air contained inside the housing. The fluorescent lamp is in contact with outside air to thereby protect the ballast circuit. This design further includes a partition plate and several vents surrounding the bowl to reduce the temperature inside the housing. Although this design provides a vent for the heat within the bowl member such that the ballast circuit is not overheated, it does not provide an air gap between the fluorescent lamp and the ballast circuit. Consequently, this design does not isolate the ballast circuit from the heat generated by the fluorescent lamp.
What is needed, then, and not found in the prior art, is a compact ballast that provides an air gap between the ballast housing and the fluorescent lamp to isolate the ballast circuit from the heat generated by the fluorescent lamp.